Gafferbill said:
Nick ......can an on the spot fine be challenged?
Yes but like all things French, you pay(see below), then appeal or reclaim the money (even for medical treatment for those in the French system)
......or instant driving bans of 6 months for exceeding a French speed limits by 50 kph?
I've never heard of that but the law is that you can't drive a motor vehicle if you are not carrying a valid license & I know that French Police will take your license if you are caught doing over 50kph over a limit, so you can't continue your journey as a driver.
If you have a non-French license you just apply for a new one when you get home saying you have lost or damaged yours. There is no collaboration between different EU licensing authorities.
......or confiscation of your car until any fine is paid?
Again I have never heard of that but wouldn't surprise me as a way of guaranteeing the fine is paid, just like the UK Police can confiscate a vehicle if they suspect it has no insurance, MoT or tax or that the driver hasn't a valid license?
As a French resident with a UK driving license there is no requirement for me to change to a French license unless I commit an offence attracting a 3 or more points.
Just after I moved here, so still had UK registered vehicles I was done for not wearing a seat belt & was given an 'on the spot fine' which meant I had to buy a 90€ stamp from the post office, stick it on the postcard the officer gave me & post it to the local Prefecture. No route marching to the bank to get cash etc. Other (speeding) offences are just a letter in the post, the same as the UK except I ignore the ones that come from the UK
In fact, I've never know anyone who has been route marched to the bank to get the cash, it's always a friend of a friend or 'someone down the pub'.